Evolution and Darwin

1. EvolutionandDarwin

2. What is evolution? X • A slow change over time • A heritable change in the characteristics within a population from one generation to the next • The development of new types of organisms from preexisting types of organisms over time

3. Evolution Primers • Isn't Evolution Just a Theory???

4. History of Evolution

5. Charles Darwin – a brief history • Born in England on February 12, 1809 • In 1831 began a 5-year journey on the HMS Beagle as a naturalist • Observations and specimen collections led him to develop “the single best idea anyone has ever had” • “Developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors” • Darwin video clip

6. Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. On the Galapagos Islands, Darwin observed species that lived no where else in the world. These observations led Darwin to write a book.

7. Darwin’s Observations 1.Species vary globally – Darwin noticed that different, yet ecologically similar, animal species inhabited separated, but ecologically similar habitats around the globe • Flightless birds (emu, ostrich, rhea) • Convergent evolution

8. Darwin’s Observations 2. Species vary locally – Darwin noticed that different, yet related, animal species often occupied different habitats within a local area • Tortoise, mockingbirds

9. Darwin’s Observations 3. Species vary over time – Darwin noticed that some fossils of extinct animals were similar to living species - fossils – preserved remains of ancient, extinct organisms Who is Charles Darwin?

10. Friends • Friends Evolution Montage

11. Ideas that Shaped Darwin’s Thinking • Lyell & Hutton – • Concluded that Earth is extremely old and that the processes that changed Earth in the past are the same processes that operate in the present (still changing) • Hutton (in 1785) – geological processes shape Earth • Lyell (in 1830) – uniformitarianism – geological processes we see in action today must be the same ones that shaped Earth millions of years ago • Lamarck– 1809 • Inheritance of Acquired Characteristics • Organism could change during their lifetimes by selectively using or not using various parts of their bodies; then pass these acquired traits on to their offspring, enabling species to change over time  • One of the first naturalist to suggest that species are not fixed  • One of the first to try and explain evolution scientifically using natural processes  • Recognized that there is a link between an organism’s environment and it’s body structures 

12. “The Inheritance of Acquired Characteristics”Lamarck vs Darwin • Example: -A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring. -A muscle builder will pass the muscles on to his offspring…. NOT TRUE

13. Ideas that Shaped Darwin’s Thinking • Malthus – 1798 • English economist • Reasoned that if the human population grew unchecked, there would not be enough living space and food for everyone • Artificial Selection • Nature provides variations, but humans select those they find useful

14. Artificial Selection • The selective breeding of domesticated plants and animals by man. • Question: What’s the ancestor of the domesticated dog? • Answer:WOLF • This is STELLA!!!!!

15. Darwin’s Contribution to Science Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent of common ancestors.

16. Darwin and Wallace • Same conclusion about evolution as a result of similar experiences • Influenced by Lyell and Malthus • Observed plant and animal life in several parts of the world • Wallace (1858) sent Darwin a manuscript describing “natural selection” • Wallace and Darwin arrived at the theory of Natural Selection independently, and presented their ideas in public together in 1858

17. Charles DarwinWallace kind of gets dissed • Wrote in 1859: (11/24 – pub) • “On the Origin of Species by Means of Natural Selection” • Main points: 1. Struggle for Existence (competition) 2. Variation and Adaptation 3. Survival of the Fittest 4. Natural Selection

18. Struggle for Existence • Organisms produce more offspring than can survive. (OVERPRODUCTION) • Grasshoppers can lay more than 200 eggs at a time. Only a small fraction of these offspring survive to reproduce.

19. Variations and Adaptations • There is variation in nature, and certain variations – called adaptations – increase an individual’s chance of surviving and reproducing. • Physical, physiological, and/or behavioral traits that enhance an organisms chances for surviving in its environment • Green vs. yellow color in grasshoppers is a heritable variation: green can blend into environment and avoid predators

20. Survival of the Fittest • Suggests that natural selection selects mainly for survival… IT DOES NOT • Selects for contribution of genes to future generations • Reproduction resulting in viable offspring • Selects for individuals that are able to produce the greatest number of offspring, that in turn, can survive and reproduce • Green grasshoppers have higher fitness and so survive and reproduce more often than yellow

21. Natural Selection • How Does Evolution Really Work?

22. Survival of the Sneakiest • Survival of the Sneakiest

24. Will the grey mouse or white mouse survive more easily? • Why? • What characteristic is affecting the fitness of the mice?

25. Peppered Moths:In the year 1848, 5% of the population was dark colored moths while 95% was light colored. • In the year 1895, 98% was dark colored while 2% was light colored. • In the year 1995, 19% was dark colored while 81% was light colored. • What was the reason for the changes in the number of dark and light colored moths? • In the early 1800s, England was not so industrialized yet and pollution was still low. The trees had light colored bark so the light colored moths had a better advantage and a better survival rate than dark colored ones. • In the late 1800s, England started to become more industrialized and factories increases. These factories caused trees to become soot coated, the bark was darker. The dark colored moths were then camouflaged and survived more than light colored ones. • Then in the mid 1900s, the air started to become cleaner due to clean air laws. Trees began to have light colored barks and once again light colored moths increased in the population.

26. http://www.sciencenetlinks.com/interactives/evolution.html Another example of natural selection…

27. Darwin’s Finches • A Close Look at Darwin’s Finches When Charles Darwin traveled to the Galápagos Islands, he found a variety of species of finches. Although each species was slightly different from the others, all the species were related. None of the finch species he found were similar to finches on the mainland. When Darwin saw such extensive diversity of species in a single group of birds, he hypothesized that they all could have descended from a common ancestor. His observations of these finches helped him formulate his concept of evolution. The phylogenetic tree below shows the relationships Darwin proposed among the species of finches. The tree is based on a comparison of the anatomy, behavior, and location on the island of each finch species. Look carefully at each species, and notice the dramatic difference among the beaks. Each type of finch has a beak adapted to its diet. Darwin’s finches are an example of adaptive radiation. Adaptive radiation is the emergence of many species from a common ancestor that was introduced to various new environments. For adaptive radiation to occur, the new environments must offer new opportunities and pose new problems of survival for the species. • Which of the ground finches illustrated above would be able to eat the largest, toughest nuts and seeds? Explain your answer. • Study the insect-eating finches shown in the diagram. What can you infer about the insects of the Galápagos Islands?

28. What does Darwin’s mechanism for evolution suggest about living and extinct species??? • All organism descended from a common ancestor • “Descent with modification” • Homer Evolution

29. Evidence for Evolution • Biogeography • Fossil Record • Comparative Anatomy • Developmental Biology • Comparative Biochemistry • How Do We Know Evolution Happens?

30. Biogeography – study of where organisms live now and where they and their ancestors lived in the past • Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors • Closely related species differentiate in slightly different climates • Very distantly related species develop similarities in similar environments Adaptive Radiation • Evolutionary process that gives rise to new species adapted to new habitats and ways of life

31. The Age of the Earth and Fossils • The Age of the Earth • Earth had to be old enough for these proposed changes to occur – plenty of time for Natural Selection • Earth is ~4.5 byo (determined by radioactive dating) – plenty of time for natural selection to take place • Fossils discovered after Darwin fill in some of the “gaps” in the fossil record • One fossil shows the evolution of whales from a land-based mammal (book figure 16-3)

32. Comparing Anatomy and Embryology • Homologous Structures • Parts that are similar in structure but different in function • Humans, penguins, alligators, bats all have the same bones in their arms but they are used for different things • Similar Embryos • Embryos of different organisms are very similar and have similar structures early on • Must have similar proteins at work • Vestigial Structures • Structures that are so reduced in size or function that they are merely traces of similar organs in other species (I.e. tailbone and appendix in humans) • Analogous Structures • Parts that are similar in function but not structure • i.e. Wing of bee, bird, bat

33. Genetics and Molecular Biology • All organisms have DNA • Therefore similar RNA, similar genes, and similar proteins • All organisms have ATP

34. Evolution of Populations Ch 17 • Process of change over time • A change in the genes!!!!!!!!

35. Population Genetics • The science of genetic change in population. • Population – all the members of a species that occupy a particular area at the same time • Gene Pool – all the genes in all the members of a population

36. Genes and Variation • Genetics Joins Evolutionary Theory • Variation is the raw material for natural selection • Gene pool – consists of all the genes, including all the different alleles for each gene, that are present in a population • Relative frequency – the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur • Therefore – evolution is any change in the relative frequency of alleles in the gene pool of a population over time • 3 Sources of Genetic Variation • Mutations • Genetic Recombination in Sexual Reproduction (Ind assortment and crossing over) • Lateral Gene Transfer (conjugation) • Single-Gene (2 pheno) vs. Polygenic Traits (many pheno/bell curve) ***Natural Selection acts directly on PHENOTYPES not actual alleles*** some phenotypes are better suited to an environment than others and they will survive, reproduce and pass on their genes.

37. Evolution as Genetic Change in Populations How Natural Selection Works – 3 Types Stabilizing Selection • Individuals with the average form of a trait have the highest fitness • Represents the optimum for most traits • Results in a similar morphology between most members of the species Directional Selection • Individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait • A shift in one direction • Peppered moth Disruptive Selection • Individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait • A shift in both direction, away from the center • Shell color (dark rocks and light sand)

39. Genetic Drift • Random changes in the frequency of a gene in the absence of natural selection  occurs because of CHANCE • Occurs efficiently in small populations because small changes affect more members • Two examples: a. Bottleneck effect b. Founder effect

40. Genetic Drift

41. a. Bottleneck Effect • Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size. • Examples: 1. Earthquakes 2. Volcano’s

42. b. Founder Effect • Genetic drift resulting from the colonization of a new location by a small number of individuals. • Results in random change of the gene pool. • Example: 1. Islands (first Darwin finch)

43. Hardy-Weinberg Principle • Genetic Equilibrium – situation in which allele frequencies in the gene pool of a population remain constant • The concept that the shuffling of genes that occurs during sexual reproduction, by itself, cannot change the overall genetic makeup of a population. • Shows mathematically and theoretically that there are situations where evolution DOES NOT OCCUR • Seldom achieved in nature

44. Hardy-Weinberg Principle • This principle will be maintained in nature only if ALL five of the following conditions are met: 1. Very large population 2. Isolation from other populations (no immigration, no emigration) 3. No net mutations 4. Random mating 5. No natural selection Hardy-Weinberg Principle

47. Species • A group of populations whose individuals have the potential to interbreed and produce viable offspring.

48. Speciation • The evolution of new species. Species that occupy an otherwise unoccupied niche face no competition, they will therefore have a 100% success rate

49. Reproductive Isolation • Any mechanism that impedes two species from producing fertile and/or viable hybrid offspring -factor necessary for the formation of a new species. • Barriers: 1. Geographic (rivers, mountains) 2. Behavorial - differences in courtship behavior 3. Temporal - fertile periods (time)

50. Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change. Interpretations of Speciation